Certain downhole operations involve placement of elements in a downhole environment, where the element performs its function, and is then removed. For example, elements such as ball/ball seat assemblies and fracture (frac) plugs are downhole elements used to seal off lower zones in a borehole in order to carry out a hydraulic fracturing process (also referred to in the art as “fracking”) to break up different zones of reservoir rock. After the fracking operation, the ball/ball seat or plugs are then removed to allow, inter alia, fluid flow to or from the fractured rock.
Balls and/or ball seats, and frac plugs, can be formed of a corrodible material so that they need not be physically removed intact from the downhole environment. In this way, when the operation involving the ball/ball seat or frac plug is completed, the ball, ball seat, and/or frac plug is dissolved away. Otherwise, the downhole article may have to remain in the hole for a longer period than is necessary for the operation.
To facilitate removal, such elements can be formed of a material that reacts with the ambient downhole environment so that they need not be physically removed by, for example, a mechanical operation, but instead corrode or dissolve in the downhole environment. In order to employ dissolution or corrosion to remove downhole elements, it is very desirable to develop downhole articles and methods of their use whereby the dissolution or corrosion and removal of these elements may be selectively controlled.